Tom Kilburn

A Mathematician Who Became an Engineer

Tom Kilburn was born on 11 August 1921 in Dewsbury, Yorkshire, England. He studied mathematics at Cambridge University during the Second World War and graduated with first-class honours in 1942.

Although trained as a mathematician, Kilburn was sent into wartime electronics work at the Telecommunications Research Establishment (TRE). There he joined Frederic Williams's group and became an accomplished electronics engineer. The transition from pure mathematics to practical electronics would shape the rest of his career.

From Radar to Computer Memory

After the war, Williams moved to the University of Manchester and Kilburn joined him. They worked on a bold idea: storing binary information electronically using a cathode-ray tube, the same kind of tube used in radar displays.

Kilburn made major improvements to the technique during 1947. The resulting Williams-Kilburn tube became one of the first practical forms of electronic random-access computer memory. It could access different memory locations electronically rather than having to read through them sequentially — a crucial advantage for a computer that needed to fetch instructions and data at high speed.

The Manchester Baby

Kilburn led the detailed work designing and building the Small-Scale Experimental Machine — the Manchester Baby — to test the new CRT memory. Geoff Tootill worked closely with him, and Frederic Williams headed the wider research project.

Kilburn wrote the first program executed by the Baby. The program searched for the highest factor of a number. On 21 June 1948 it ran successfully — the first time an electronic digital computer had executed a program stored electronically in its own read-write memory.

The Baby was primarily an experiment to prove that the new memory worked. But its success opened the door to practical electronic computing. The achievement belonged to the three core team members: Williams, Kilburn and Tootill.

Atlas and Virtual Memory

Kilburn then became the principal driving force behind Manchester's computer-development programme. His teams worked on a sequence of pioneering machines, each more powerful than the last.

One of the most significant was Atlas, completed in the early 1960s. Atlas helped pioneer concepts including paging and virtual memory — techniques that allowed a computer to manage information between fast and slow storage in a way that made a larger apparent memory available to programs. These ideas became fundamental to modern computing. Atlas was a substantial team project, and Kilburn should not be described as inventing virtual memory entirely alone.

Building a Department and a Legacy

Kilburn became Professor of Computer Engineering at Manchester in 1960. In 1964 he became head of the new Department of Computer Science — one of the first such departments in the world. He remained a major figure in Manchester computing until retiring in 1981.

The University of Manchester records that Kilburn was a keen Manchester United supporter who enjoyed football, jazz and playing the piano. He never became known for owning or using a personal computer, despite having helped create the modern computing era.

Kilburn was elected a Fellow of the Royal Society in 1965, received a CBE in 1973, the Royal Medal in 1978, and the Eckert-Mauchly Award in 1983. He died on 17 January 2001 in Manchester.